In recent years, as a content delivery technology using HyperText Transfer Protocol (HTTP), Moving Picture Experts Group-Dynamic Adaptive Streaming over HTTP (MPEG-DASH) was standardized (for example, see Non-Patent Literature 1). MPEG-DASH adopts an adaptive bitrate streaming (ABS) technology in which a plurality of pieces of encoded data in which the same content is expressed at different bit rates are stored in a content server and a client selects and reproduces one piece of encoded data among the plurality of pieces of encoded data according to a network bandwidth.
Incidentally, selecting a partial image which is a part of an image instead of the entire image and delivering it adaptively has been considered. For example, delivering a partial image which is a part selected in the entire image on a terminal side receiving image data, or controlling the size of the partial image to be delivered according to the performance of the terminal (for example, a processing ability of a CPU or the like or the size of a display), a transmission path, a load situation of a server, or the like has been considered.